This invention relates to plasma generation by electron cyclotron resonance (ECR).
In ECR, energy from the electric field of microwave radiation is absorbed by electrons of a selected gas within an evacuated source chamber, causing the gas to ionize. A magnetic field established within the chamber causes the electrons to traverse circular orbits in the manner of a cyclotron. The electrons collide with and ionize other gas molecules to form the plasma. If the magnetic field matches the microwave frequency (e.g., 875 Gauss for a microwave frequency of 2.45 GHz), the orbital frequency of the electrons is resonant with the microwave frequency. Then the electrons absorb microwave energy very efficiently, producing high electron and high ion densities, at relatively low microwave power.
ECR generated plasma streams are useful, for example, in low energy ion beam etching and thin film processes.